Work Zone Mobility and Safety Program

Anderson Junction to Black Ridge

slide 1

CA4PRS Case Study

Cameron Kergaye, PhD, PE – UDOT
Brad Lucas, PE, PTOE – UDOT
Troy Torgersen, PE – UDOT
Eric Malmberg, PE – Wilson & Company


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slide 2

Project Location

  • Southwest Utah
  • 21 miles N of St. George, UT
  • 141 miles NE of Las Vegas, NV
  • Between Milepost 27 & 34

Map of Western United States with the State of Utah highlighted.

slide 3

Project Location

  • Southwest Utah
  • 21 miles N of St. George, UT
  • 141 miles NE of Las Vegas, NV
  • Between Milepost 27 & 34

Map of the state of Utah with major Interstates identified. The area between Cedar City and Saint George on I-15 has a circle around it.

slide 4

Project Location

  • Primary Freight Corridor
  • 2500+ Trucks per day
  • 21% to 33% Truck Traffic

Map of the roadways across the Western United States with the major freight corridors highlighted in blue. The state of Utah is outlined and its freight corridors are highlighted in red.

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Project Location

  • Primary Freight Corridor
  • 2500+ Trucks per day
  • 21% to 33% Truck Traffic

Map of Utah with the major freight corridors color coded to indicate the range of trucks per day that travel on each roadway.

slide 6

Existing Roadway Characteristics





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Existing Roadway Characteristics

  • Rural two-lane freeway with variable width median
  • Two 12 ft lanes in each direction
  • 4 ft left shoulders and 10 ft right shoulders

Diagram of the distribution of I-15 roadway characteristics from the street-level. Diagram shows that the roadways in each direction contain a 10 ft-wide right shoulder, two 12 ft lanes, and a 4 foot left shoulder separating the travel lanes from the median.

slide 8

Existing Roadway Characteristics

  • Asphalt Pavement
  • Rolling to Mountainous terrain with grades between 3% - 6%
  • 4 – Interchange Structures within project limits


slide 9

Proposed Pavement Rehabilitation

  • 2" Mill
  • 3" Cold-in-place recycle
  • 1 ½" HMA
  • 1 ½" SMA


slide 10

Proposed Pavement Rehabilitation

  • Dig out and replace 15" of asphalt at existing structures to meet AASHTO vertical clearance at underpass structures
  • Improve ramp geometry and lengths
  • Construction Schedule: (between June and October 2010)


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Existing Traffic Conditions

  • AADT ≈ 21,760 (2009)
  • 21% Trucks (4% single & 17% Combo Trucks)
  • Monthly Hourly Traffic Reports obtained from UDOT (2009)
  • Three months selected for Traffic Pattern Comparison (April, August, & October)


slide 12

Existing Traffic Conditions Southbound


Graph indicates that traffic volume is greatest (above 800 VPH) across weekdays and weekends during the hours from 1 p.m. to about 8 p.m.

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Existing Traffic Conditions Northbound


Graph indicates that traffic volume is greatest (above 800 VPH) across weekdays and weekends during the hours from 1 p.m. to about 8 p.m.

slide 14

Goals and Objectives for using CA4PRS

  • Compare construction strategies to optimize staging plans
  • Reduce construction schedule
  • Develop less disruptive lane closure schemes and traffic management plans
  • Minimize total project cost


slide 15

Construction Alternatives

  • Median Crossover Closure

Image depicts the closure of the northbound lanes for construction. Northbound traffice is diverted over a median cross-over and the left southbound lane of interstate is used for northbound traffic. A temporary barrier is used to divide the two lanes of traffic that are traveling in opposite directions. Another median crossover is used to channel northbound traffic back into the northbound lanes downstream of the work zone.

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Construction Alternatives

  • Median Crossover Closure
  • 24/6 Closure (Open on Sundays)

Diagram depicts the right lanes of both the northbound and southbound roadway closed for work zones, leaving only the left lane open for throught traffic in each direction.

slide 17

Construction Alternatives

  • Median Crossover Closure
  • 24/6 Closure (Open on Sundays)
  • Nighttime Closure (7pm to 5 am)


slide 18

Summary of CA4PRS Analysis Results


Snapshot of a table that provides characteristics of lane closure alternatives. The alternative with the lowest cost is the 24/6 alternative.

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Summary of CA4PRS Analysis Results

  • CA4PRS indicated that the Median Crossover closure alternative provides the shortest project construction Schedule but not necessarily the least impacts to traffic. Also, the Road User Cost and Total Project Costs were higher given the extra traffic control costs and expenses to build the crossovers.
  • CA4PRS indicated that both the 24/6 closure alternative and the Nighttime Closure Alternative minimized work zone traffic delay and lowered the road user cost and traffic control costs.


slide 20

Observations

  • During Peak hours, actual delays & queues were larger than predicted

Graph shows that I-15 northbound volumes during lane closure on Thursday were above 600 vph from 9:00 a.m. to 6:00 p.m., and above 800 vph from 11:00 a.m. to 2 p.m. On Friday, volumes exceeded 600 from 8:00 a.m. through about 12:30 p.m. and exceeded 800 vph from 10 a.m. through about 11:30 a.m.

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Observations

  • During Peak hours, actual delays & queues were larger than predicted

Graph shows that on 6/30, speeds dropped steadily from 70 mph at 11 a.m. to less than 10 mph by 1:00 p.m. Speeds did not accelerate above 10 mph until after 6:00 p.m. and did not reach full speed until after 9:00 p.m. Conversely, speeds on 7/1 were consistently maintained at or above the speed limit all day.

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Observations

  • During Peak hours, actual delays & queues were larger than predicted
    • Unexpected results came from errors in data entry
      • Percentage of Truck Traffic (2009 data shows ≈ 21% ; actually observed closer to 33% or higher)

Screen shot of a capacity adjustment screen that depicts a before construction and during construction capacity usage breakdown. A red circle highlights before and during construction percentage of single lane basic capacity for trucks. Before construction 10 percent of single lane basic capacity was used by trucks. During construction, 21.7 percent of single lane basic capacity (vphpl) was used by trucks.

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Observations

  • During Peak hours, actual delays & queues were larger than predicted
    • Unexpected results came from errors in data entry
      • Factor for Passenger Car Equivalent (Level= 1.5, Rolling =2.5, or Mountainous Terrain = 4.5)

Screen shot of a capacity adjustment screen that depicts a before construction and during construction capacity usage breakdown. A red circle highlights before and during construction percentage of single lane basic capacity for passenger car equivalents. Before construction, PCE for a single-lane was 1.5. During construction, PCE for a single lane remained 1.5.

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  • During Peak hours, actual delays & queues were larger than predicted
    • Unexpected results came from errors in data entry
      • Traffic Control setup (10 ft lanes with no shoulders)

Screen shot of a capacity adjustment screen that depicts a before construction and during construction capacity usage breakdown. A red circle highlights before and during construction percentage of single lane basic capacity for passenger car equivalents. Before construction, PCE for a single-lane was 1.5. During construction, PCE for a single lane remained 1.5.

slide 25

Observations

  • During Peak hours, actual delays & queues were larger than predicted
    • Unexpected results came from errors in data entry
      • Police activity and speed enforcement impeded traffic


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Observations

  • During Peak hours, actual delays & queues were larger than predicted
    • Unexpected results came from errors in data entry
      • Lengths of contractor operations adjacent to traffic was a distraction to drivers


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Observations

  • During Peak hours, actual delays & queues were larger than predicted
    • Unexpected results came from errors in data entry
      • Factor for Passenger Car Equivalent (Level= 1.5, Rolling =2.5, or Mountainous Terrain = 4.5)
      • Percentage of Truck Traffic (2009 data shows & 21% ; observed closer to 33% or higher)
      • Traffic Control setup (10 ft lanes with no shoulders)
      • Police activity and speed enforcement impeded traffic
      • Lengths of contractor operations adjacent to traffic was a distraction to drivers


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Observations

  • During Peak hours, actual delays & queues were larger than predicted
    • Unexpected results came from errors in data entry
    • When the data was entered correctly, the calculated results better reflected the observed conditions


slide 29

Lessons Learned

  • Avoid exceeding capacity by using a factor of safety
  • Develop support from DOT management regarding implementation of CA4PRS recommendations
  • Use detailed and relevant traffic data for input variables
  • Use Real-Time data to make adjustments
  • Consider a Performance Based Work-Zone specification
  • Listen to the recommendations of the Resident Engineer for paving operations


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Conclusions

  • CA4PRS results and recommendations were useful when the program is used correctly.
  • Be sure to evaluate the project entirely and consider even minor factors to be relevant and influential.
  • Develop confidence and familiarity in the use of the CA4PRS program.

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